1. Field of the Invention
The present invention relates to a motor driving apparatus.
2. Description of the Related Art
As a cooling fan motor, a spindle motor configured to rotationally drive an optical or a magnetic disk, or a capstan motor employed in a tape recording apparatus, a DC motor is employed. Typical DC motors each include a rotor having a permanent magnet and a stator having a coil. By controlling electric current to be supplied to the coil, such a DC motor is rotationally driven.
In order to detect the rotational position of the rotor of the DC motor, a Hall sensor (Hall element) is employed. Such a Hall sensor generates a pair of Hall signals that change in a complementary manner according to the position of the rotor of the motor (which will be collectively referred to simply as a “Hall signal”). Hall sensor mounting motors are known including a Hall sensor mounted on a stator.
A motor driving circuit switches the polarity of the driving voltage to be supplied to the coil based upon the Hall signal, and uses the Hall signal to generate a control signal for controlling a regeneration period. In a case in which such a Hall signal has a sine waveform or a trapezoidal waveform according to change in the magnetic polarity of the rotor, the motor driving circuit is capable of gradually changing the driving voltage and the magnetic polarity to be applied to the coil using the change in the voltage of the Hall signal detected before and after each switching timing, thereby providing reduced motor driving noise. Such an arrangement is also referred to as “soft switching”.